This invention relates to an electronic musical instrument, and particularly an accompaniment tone generator therefor.
It is already known as a single finger mode in the automatic bass/chord performance that a desired key on the keyboard is depressed as a key for designating a root note so as to automatically produce simultaneously a plurality of tones in the predetermined interval (for example 1, 3, or 5 degrees) with respect to the designated root note, or a chord tone. It is also already known that there exists an automatic bass tone production device which automatically produces a bass tone with a note having interval of number of degree shown by automatic bass pattern data from the root note detected among chord constituting notes. The conventional accompaniment tone production device such as chord production device for single finger mode or automatic bass tone production device has a defect that the circuit configuration is of a large scale, because the device needs a read-only-memory (ROM), or an arithmetic circuit for processing parallel coded signals of plural bits.
More concretely, the chord production device which automatically produces plural tones, or chords, in the predetermined interval (1, 3 or 5 degrees) to a root by depressing a desired key on the keyboard as a key for designating a root is already known as a device for the single finger mode in the automatic bass/chord performance. In this conventional type of chord production device, the following two were mainly thought as methods for the automatic production of a plurality of chord-constituting tone data on the basis of a depressed key for designating a single root note: One of them is a method which comprises a read-only-memory storing each of the notes corresponding to chord-constituting tones of various chords (major, minor, seventh, etc.) when each of the 12 note names (C to B) is made to be a root, and reads out respective note data of each chord-constituting tone from said read-only-memory on the basis of single root note data designated by depressed key. This method, for example, is used in the U.S. Pat. No. 4,065,993.
Another method is to express the root note designated by a depressed key in the coded signal of plural bits and to obtain the coded signal which represents the note of desired chord-constituting tone having an interval equal to an augmented data from the root tone by adding (or subtracting) the augmented data corresponding to the difference of intervals between the root tone and desired chord consituting tone (accompaniment tone) to the root note data. This method, for example, is used in the U.S. Pat. No. 4,228,712. This method does not require above mentioned read-only-memory but can be applied only for an electronic musical instrument of the type which processes data of depressed keys by converting said data into the coded signal of plural bits and requires an arithmetic circuit for addition and substraction and a circuit for the generation of the augmented data.
Further, with respect to the conventional automatic bass performance system, as methods for the production of bass tone data of the degree represented by automatic bass pattern data, the following two were mainly thought of: One of them is a method which reads out successively note data (coded signal which represents a note name) corresponding to various degrees (1, 3, 5, 7, etc.) from the read-only-memory on the basis of root note data which represents the note name of root of accompaniment chord), and selects a note data corresponding to the degree represented by bass pattern data from among the note data which are read out. This method, for example, is used in U.S. Pat. No. 4,192,211.
Another is a method which expresses the root note of accompaniment chord in the coded signal of plural bits, expresses bass pattern data in augmented data corresponding to a desired interval, and obtains the coded signal of note having the interval equal to said augmented data from the root note by adding (or subtracting) the augmented data to the root note data. This method is used in the aforesaid U.S. Pat. No. 4,228,712.
This method does not require the aforesaid read-only-memory but requires an addition and subtraction circuit for plural bits. Furthermore, it is easily applied to such a type of electronic musical instrument which processes depressed key data by converting such data into the coded signal of plural bits, but it is difficult to be applied to other types of electronic musical instruments (for example, an electronic musical instrument of the type that processes depressed key data as a time division multiplex data of one bit).